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| EPoS Contribution |
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Magnetic Fields and Star Formation - Recent CARMA Observations
Dick Crutcher U Illinois, Urbana IL, US | |
| The many possible roles of magnetic fields in star formation remain unclear, requiring observations of magnetic fields at all stages and conditions to further our understanding. Here I present three very recent (post-TADPOL) CARMA 1.3-mm spectral-line and continuum polarization observations that probe three different areas of star formation: 1) Zeeman observations provide the only direct measurement of magnetic field strengths in molecular clouds. Earlier single-dish CN Zeeman N=1-0 measurements were with 23" resolution; needed now are higher angular resolution Zeeman maps of magnetic field strengths. Our CARMA Zeeman-effect commissioning observations reported here were carried out for the N=2-1 CN transitions with ~3” resolution toward W3OH and DR21OH. These are the first interferometric CN Zeeman observations of dense molecular cores. 2) Our CARMA dust polarization maps of the Class 0 low-mass protostar L1157-mm show magnetic field lines aligned with the outflow and suggest a full hourglass magnetic field morphology centered about the core (only the second well-defined hourglass detected around a low-mass protostar to date). Plane-of-sky magnetic field strengths are ~ 2 mG (supercritical). This protostellar region thus appears to match standard models of protostar formation that include magnetic fields. 3) Observations of magnetic fields in the disks of T Tauri stars are essential to test theoretical models, such as MHD turbulence driven by MRI instability or a magnetically driven wind from a disk. Our CARMA dust polarization observations of HL Tau have achieved the first RESOLVED polarization detection of a T Tauri star disk. The data suggest a toroidal field morphology, which is the predicted morphology if MRI is the dominant mechanism for angular momentum redistribution inside the disk. Results of these three observational projects will be presented with discussion of the astrophysical implications and the implications for future ALMA observations. | |
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| Caption: LEFT: L1157-mm. Greyscale is Spitzer 8 micron intensity from the disk, red (>3 sigma) and yellow (2-3 sigma) bars are magnetic field directions, red line is the axis of the possible hourglass magnetic field, black line is the central axis of the CO outflow, black contours are CO outflow, cyan contours are CARMA 1.3-mm dust intensity. Insert shows inner region. RIGHT: HL Tau. Dotted line is the disk major axis PA, bars are magnetic field directions (red > 3 sigma up to ~8 sigma, blue 2-3 sigma), contours are total intensity, greyscale is polarized emission. Beam is 0.6”; a higher resolution map should be available by the meeting. | |
| Collaborators: I.W. Stephens, U Illinois, US L.W. Looney, U Illinois, US W. Kwon, U Illinois, US M. Fernandez-Lopez, U Illinois, US N. Hakobian, U Illinois, US R.L. Plambeck, UC Berkeley, US C.L.H. Hull, UC Berkeley, US |
Key publication
Suggested Sessions: Magnetic Fields |